U.S. Pat. No. 6,234,648 discloses a light system in which blue LEDs and red LEDs are used together with a phosphor that converts the radiation of the blue LED into green radiation.
DE 10 2010 034 913 discloses materials for LEDs having a temperature-dependent refractive index. The definitions used therein for operating temperature, refractive index and change in the refractive index as thermo-optical coefficient dn/dT shall also be applied hereinafter.
There is a need to provide a light system whose color impression remains as stable as possible at different temperatures. The different temperatures often arise in the start-up phase of operation or in different environments. A white color impression is preferred, but a colored color impression is not ruled out.